1. Field of the Invention
The present invention relates to an automatic steering system for a vehicle, for automatically parking the vehicle without recourse to steering by a driver.
2. Description of the Prior Art
Automatic steering systems for vehicles are already known from Japanese Patent Application Laid-Open Nos. 3-74256 and 4-55168. The automatic steering systems for vehicles utilize an actuator of a conventionally well-known electric power steering device, and are designed so that reverse parking and linear parking are automatically controlled by controlling the actuator based on the relationship between a traveling distance of the vehicle and a steering angle that are previously stored.
The automatic steering is carried out with driver's hands released from a steering wheel. For this reason, when the driver further moves the vehicle backwards after the vehicle has reached a target position to finish the automatic steering control, the vehicle is brought into a "no hands" driven state. At this time, if there is an undulation in the road surface, if the friction coefficient of a road surface contacted by left and right wheels is not uniform, or if a torsional deformation remains in a tire after the steering, there is a possibility that the steering wheel is turned, so that the vehicle is moved in an unintended direction.